Chapter 21

Question 1

What are electromagnetic waves (EM waves)?

What are their speed?

Answer 1

EM waves are produced by electric charges that are accelerating
The accelerated charges generate changing (oscillating) electric and magnetic fields
The oscillating electric and magnetic waves are coupled together and propagate as an electromagnetic wave (transverse waves!!)

Speed is equal to speed of light
C=3.00x10^8 m/s

Slide 23 and 25 Feb 7

Question 2

What are the order of electromagnetic waves from smallest wavelength to largest?
What are cosmic microwaves?

Answer 2

Gamma Rays- high energy photons (produces during energy transitions in nuclei)
X- rays- produced by deceleration of electrons interacting with matter
Ultraviolet- potentially hazardous (sunburn, skin cancer, cataracts) also useful
Visible light- 700nm to 400nm, peak wavelengths emitted by sun
Infrared- thermal radiation at room temp
Microwaves
TV, FM
AM

Question 3

What are cosmic microwaves?

Answer 3

Cosmic microwave background radiation is a remnant if the Big Bang
WMAP was sent to space to measure background radiation (found universe is made of 4.6% atoms, 24% dark matter, 71.4% dark energy)